The present invention provides a substrate dry device and a method for drying the substrate, the substrate dry device comprises a cavity, dry bars and a sensor disposed on the top of the cavity, liquid immerging the substrate is accommodated within the cavity, with the dry bars comprising a first dry bar and a second dry bar arranged parallel to each other, with a gap is formed therebetween and with the sensor disposed on one end or on two ends of the gap for monitoring a position in which the substrate is moved away from the liquid. By use of the above arrangement, the gas is ejected through the dry bars to the surface of the substrate which has moved away from the liquid, the tension of the surface of the liquid film on the substrate is changed by marangori effect under the action of the gas and the surface tension gradient of the liquid film makes the liquid film shrink so that the surface of the substrate becomes dry.